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The Summer Triangle, a signpost for all seasons

Tonight for March 16, 2015

As seen from our northern temperate latitudes, the three brilliant stars of the Summer Triangle – Vega, Deneb and Altair – are out for at least part of the night every night of the year. Presently, the Summer Triangle shines in the eastern predawn/dawn sky. You can often see this star formation from light-polluted areas.

On a moonless night, an edgewise view of the galactic disk – and the Dark Rift – pass right through the Summer Triangle. Photo credit: cipdatajeffb

Like the Big Dipper, the Summer Triangle is an asterism – a pattern of stars that is not one of the officially recognized 88 constellations. To gauge the size of this signpost star formation, hold a ruler an arm’s length from your eye. The ruler pretty much fills the gap between Vega and Altair, the Summer Triangle’s first and second brightest stars, respectively.

Like all the stars, the stars of the Summer Triangle rise four minutes earlier every day, or two hours earlier every month. Why is this happening? It’s happening because Earth is orbiting the sun, and our night sky is pointing out on an ever-changing panorama of stars.

Around May Day – May 1 – the Summer Triangle will climb over the eastern horizon around local midnight (1 a.m. daylight saving time). When middle to late June comes rolling along, you’ll see the Summer Triangle sparkling in the east at evening dusk – a sure sign of summer’s return to the Northern Hemisphere.

Bruce McClure is the chief writer for the popular EarthSky Tonight pages. Since joining EarthSky in 2004, he has written thousands of astronomy articles, enjoyed here by millions. He also writes, gives planetarium shows and hosts a wide assortment of public astronomy programs in and around his home in upstate New York. If you ask an astronomy question on our site, it’s likely to be Bruce that answers it. His love for the heavens has taken him to Lake Titicaca in Bolivia, and he has sailed the North Atlantic, earning his celestial navigation certificate through the School of Ocean Sailing and Navigation. Bruce is also a sundial aficionado. He says his number one passion - besides his wife Alice - is stargazing.